A man accused of driving under the influence and crashing his pickup truck into a group of people celebrating Independence Day on the Lower East Side last year faced emotional testimony as his trial for four counts of murder began in Manhattan on Monday.

Daniel Hyden, 44, listened quietly in the courtroom as friends and family of the four victims recounted the tragic events. Prosecutors allege that Hyden ran a stop sign, drove onto the curb, and crashed his Ford F-150 through a fence into Corlears Hook Park last summer. The testimonies were given in Manhattan Supreme Court.

Liliana Ruiz, 51, was visibly shaken as she shared the harrowing experience of rushing to help her 30-year-old daughter, who was trapped beneath Hyden’s vehicle. She described the moment as she watched her daughter’s life slip away.

“I was tapping her face,” Ruiz recounted through tears, struggling to articulate the moment she tried to keep her daughter conscious. She described her daughter’s eyes as “like saucers” and noted her lips turning purple.

“‘Emily, it’s going to be okay. … Don’t close your eyes,’” Ruiz recalled saying, choking up as she realized she was witnessing her daughter’s final moments.

After the paramedics arrived, Ruiz said she went home to collect items to take to the hospital, while Emily’s young son, in a state of panic, suggested they bring a first aid kit.

“He tells me, ‘I don’t want my mom to die. She’s a great person,’” Ruiz quoted her grandson through tears.

The elder Ruiz said she faced every mother’s worst nightmare when doctors declared her daughter brain dead at Bellevue Hospital.

“What choice did you make?” Assistant District Attorney Matthew Bogdanos asked Ruiz.

“To let her go,” Luiz said, sounding inconsolable.

Killed in the crash along with Ruiz were Hernan Pinkney, 38, his mother, Lucille Pinkney, 59, and Ana Morel, 43. Seven others, including children, were injured, prosecutors say.

Hyden has pleaded not guilty to four counts of second-degree murder, aggravated vehicular homicide, and related counts and could spend the rest of his life in prison if convicted.

He’s accused of plowing into the park near the Vladeck Houses with a blood alcohol content more than double the legal limit less than an hour after he’d been escorted off nearby Pier 36 after crew aboard the Boss Lady NYC said he was too drunk to sail, as the Daily News previously reported.

In court Monday, the man’s lawyer, Theodore Herlich, posited that Hyden didn’t slam on the brakes because he’d injured his foot earlier in the evening, not because he was drunk.

In his opening statement, Bogdanos quoted from Hyden’s book, written after he’d supposedly battled his addictions and implausibly titled, “The Sober Addict: A Guide on How to Be Functional With the Dysfunctional Disease of Addiction.”

“‘A real danger to others, my bike and myself when I was on the road intoxicated,’” the prosecutor read from the book, saying Hyden had clearly been aware of the risks of driving while drunk and consciously did so anyway.

State Supreme Court Justice April Newbauer, presiding over the bench trial, also heard Monday from Hector Moreno, Hernan Pinkney’s childhood best friend, who was at the Independence Day celebration.

Moreno identified several of those killed joyfully laughing and dancing in cell phone footage taken at the barbecue hours before the incident. Testifiying he was still in severe pain after dislocating a herniated disk in the crash, Moreno said he didn’t see Hyden coming, but heard him revving his engine.

Moments after the slaughter, Moreno said, he rushed to the driver’s window, finding a disoriented-looking Hyden with his foot on the gas, shirtless and without a seat belt on and trying to move the shift gear — while several victims remained trapped under his vehicle.

“I just started hitting him as hard as I could,” Moreno testified.

Asked to identify the driver, Moreno stared down Hyden in court and pointed his finger straight at him, telling Newbauer he had no doubt.

The trial continues Tuesday.